This invention relates to apparatus for the removal and collection of particulate and fibrous matter. The apparatus is particularly intended for use as an asbestos removal system, but has a broader application to the removal of particulate and fibrous matter generally.
For convenience, reference will be made throughout this specification to asbestos and asbestos removal. However, it should be understood that this reference is as an example only.
In some applications, the matter being collected may be toxic or otherwise harmful to people or the environment, so the escape of the solid matter must be prevented. This is the case with asbestos removal systems, for example.
The potential health problems associated with asbestos fibers, especially the "fines" or very short fibers, have become very well publicized, leading to extensive efforts to remove asbestos insulation from buildings and other sites. Typically, the asbestos is stripped from the walls and ceilings, and then collected for disposal, by workers wearing suitable protective clothing and breathing apparatus.
There is thus a need for apparatus which can effectively collect the stripped asbestos fibers, without permitting the fines to escape into the environment.
The obvious way to deal with the collection of asbestos and asbestos fibers is with, in effect, a large vacuum cleaner equipped with suitable filters. This indeed has been attempted in various configurations in the prior art. However, since the filters tend to become clogged very rapidly, they require frequent cleaning. Problems in the past have included how to clean the filters efficiently, how to clean the filters without shutting down operations, and how to avoid the escape of asbestos fibers during the filter cleaning process.
It is highly undesirable to have to shut down operations for filter cleaning. Accordingly, there are prior art systems in which filters may undergo continuous or periodic cleaning by means such as vibration or mechanical cleaning, or by the use of pulsed air jets directed back through the filters. Such cleaning means suffer from the fact that the filter remains in operation during the cleaning, which greatly reduces the effectiveness of the cleaning; debris stripped from the filter tends to be drawn right back to the filter by the gas stream.
There is thus a need for apparatus in which cleaning of filters can be conducted more effectively, without needing to shut down the operation of the system. The need is particularly evident in applications such as asbestos removal, where large volumes of solid matter are involved, since the filters tend to become clogged very rapidly and thus require frequent cleaning.
Related to the problem of clogging of filters is the inability of prior art systems to operate at sufficiently high suction (i.e. low pressure, or large pressure differential below ambient pressure). One reason for this inability is the large pressure differential across the filters as they become clogged. Another reason relates to the difficulty of sealing the system to maintain the high suction (low pressure). It has to be possible to remove the asbestos from the system without seriously affecting the operating pressure.
Being able to operate at high suction (low pressure) means being able to run a longer intake hose and means better performance in terms of system throughput, resulting in reduced operating costs in general and labor costs specifically. In addition, where the asbestos is being removed from a building, the lower operating pressure makes it easier to maintain the desired pressure differential between the inside and outside of the building from which the asbestos is being removed.